Monday, First Week in Lent
Olbers’ Paradox
The heavens declare the glory of God, and the firmament shows his handiwork. — Psalm 19:1
There are a number of jokes that start with a child asking an adult, “Why is the sky blue?” But to the best of my memory, I’ve never heard any child ask, “Why is the sky dark at night?” Both questions turn out to have very interesting answers, but the latter question has much deeper implications.
The answer to the question about the dark sky at night requires us to think a bit about what we know of the universe. Prior to the last century, scientists of the Enlightenment believed the universe had always existed and was of infinite extent. But that infinity of scale creates a problem when we think about our dark night sky. Imagine you are standing deep in the woods of a forest. The foliage and the undergrowth are so thick that no matter what direction you look, you see a green leaf. In the deepest parts of the forest, or in a fully grown rain forest, it is impossible to see the horizon or sometimes even the sky. The forest floor is kept in a perpetual twilight even in the middle of the day, because wherever you are standing, eventually there’s a plant with a leaf blocking your view of the blue sky.
Now imagine you’re standing in the middle of the desert looking up into the night sky. You see that the sky is filled with stars, each one a small point of light. In part of the sky, when we look out into the plane of our own galaxy, the stars appear so close together that it looks like there is a glowing cloud that stretches all the way around the sky. That cloud of light appears because as we look into the heart of our Milky Way Galaxy, our line of sight eventually finds a star that blocks it from looking further.
If the universe is of infinite extent, then it stands to reason that no matter where we look in the sky, we will eventually see a star. The star may be very, very far away and we may see only a tiny, tiny bit of its light, but if you multiply even a tiny number by infinity, you still get infinity. So, no matter how little light we see from one star, the total amount of light that we see should be very, very bright—as if we were looking directly at the surface of the sun at noontime.
The fact that we see a darkened sky at night when logically we shouldn’t is called Olbers’ Paradox. A number of scientists and philosophers have tried to work out a resolution to this contradiction from the time Heinrich Olbers first proposed it. Interestingly enough, the writer Edgar Allen Poe first pointed the way to resolving the paradox. He suggested that the only way to understand what we see in the darkness of the night was to conclude that the universe was not infinite. It either had an edge—something scientists didn’t want to accept—or it must have had a beginning. If it had a beginning, then even if the universe is infinite, because the speed of light isn’t, we can’t see all of the universe. We can only see the portion that is as far away as light has traveled since the moment of the universe’s beginning—its “Genesis.”
Isn’t it extraordinary to be able to go outside at night and look up into the dark night sky and realize that the sky is dark because the universe had a beginning? The simple experience of nighttime proves to us that time had a start and that the universe has a history. Then it’s not too far a line of reason to start to wonder why the beginning happened, and what or who caused it. The dark sky invites us to wonder about the existence of the Creator.
Paying attention to the smallest things in our day-to-day existence can take us into the presence of the greatest questions and answers of human experience. Today, pay attention to what you experience and take on the spiritual discipline of asking yourself, “Why?”
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"Lent is Not rocket Science" was published by Forward Movement, a ministry of the Episcopal Church which publishes accessible low cost resources on discipleship written by the laity, clergy, and bishops of the church largely on a pro bono basis.
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"Lent is Not rocket Science" was published by Forward Movement, a ministry of the Episcopal Church which publishes accessible low cost resources on discipleship written by the laity, clergy, and bishops of the church largely on a pro bono basis.
